This invention relates generally to apparatus and methods for communicating electrical signals, such as power and data signals, in a well. This particularly includes electrically coupling two circuits in the well so that electrical signals can be communicated from one circuit to the other.
There are electrical devices that can be lowered into wells to detect downhole conditions, such as pressure and temperature. Although some of these devices may have self-contained power supplies and data storage elements so that no communication with the surface is needed, it is sometimes desirable to have such surface/well communication. For example, it is sometimes desirable to send one or more control signals from the surface to an electrical device in the well. Sometimes an energizing or recharging power signal may need to be sent from the surface to the device. Sending to the surface electrical signals encoded to represent the detected conditions is also desirable at least when trying to control or monitor what is happening downhole as events occur (i.e., in "real time") or when retrieving data previously stored in a downhole memory.
There have been proposals for establishing such communications between equipment or personnel at the surface and equipment down in the well. For example, electromagnetic communication has been disclosed. In one species, two coils, each associated with a respective circuit, are inductively linked without intermediate electrical current conductive connections being made. In another species, two coils communicate via an intermediate current loop formed by electrically contacting tool bodies carrying the circuits. Another type of communication is by direct electrical contact. That is, circuits are directly electrically connected by electric conductors so that current flows continuously from one circuit to another.
Even though various techniques for communicating in a well have been proposed or implemented, there is still the need for an improved apparatus and method. Such apparatus and method should be able to transfer electrical signals at relatively high transmission rates. The operations of such apparatus and method should not be adversely affected by fluid in the well capable of short-circuiting an electric circuit. Such apparatus should be readily reusable.